[RFI] A fun and educational RFI toy.
xxw0qe at comcast.net
Wed Feb 29 12:49:30 PST 2012
Be careful with LISNs and preamps. Turning on and off the DUT (device
under test) will create significant transients to the receiver. I have
never hurt a receiver or spectrum analyzer but have killed a couple of
preamps. The safe mechanism is to unplug the receiver from the lisn,
turn on the DUT , and then reconnect the receiver. I have seen a DUT
that draws 10A produce spikes of 30V at the receiver when turning off
the DUT. Large interfering sources will be S9+20 at the receiver (FCC
Part 18 limits for lighting devices is -59dBm) and no preamp will be
needed. However for quiet devices that you are trying to make even
quieter you might need a preamp and most low noise preamps are not well
protected against transients.
On 2/29/2012 1:33 PM, KD7JYK DM09 wrote:
> I picked up a LISN, Line Impedance Stabilization Network box from a fellow
> many years ago. This box allows me to apply power to a device under test
> and monitor any noise the device produces on the power line on a spectrum
> analyser. They are used for electromagnetic compliance testing.
> Now for the fun part!
> These boxes are very simple in design and you can connect the output to your
> You can plug any device operating on household power to the box, connect it
> directly to your radio and all you'll hear in your receiver is the garbage
> your item produces over the power lines and possibly radiates into the
> neighbourhood. Want to hear what a lightbulb produces, plug on in, fire up
> your receiver. How about a power supply for your computer? Plug it in,
> spin the dial. Doorbell transformer with an odd smell? Plug it in, fire up
> your receiver, listen to the hash and arcing... How about the noise another
> receiver produces to the first?
> It's great for learning what everything you own, and only what that device,
> Basic info:
> A search on Google brings up some designs for those that want to roll their
> own, there's a few on ebay, but they must be full of cocaine or gold bricks,
> the cheapest is about twenty times what I paid for a used one from a govt'
> contractor used to seeing big $ signs.
> RFI mailing list
> RFI at contesting.com
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